Cam follower mechanism



2, 1966 J. HANDLEY 3,263,512

' CAM POLLOWER MECHANISM Filed Feb. 5, 1964 4 Sheets-Sheet 1 FIG. I

INVENTOR JOHN HAN DLEY ATTO R N EYS Aug. 2, 1966 Filed Feb 5, 1964 J. HANDLEY CAM FOLLOWER MECHANISM 4 Sheets-Sheet 2 INVENTOR JOHN HANDLEY Jamar, W JM ATTORNEYS 2, 1966 J. HANDLEY 3,263,512

CAM FOLLOWER MECHANISM Fileu Feb 5, 1964 4 Sheets-Sheet 5 FIG. 3A

INVENTORS JOHN HANDLEY BY M y wm ATTORNEYS 2, 1966 J. HANDLEY 3,263,512

CAM FOLLOWER MECHANI SM Filea Febv 5, 1964 4 Sheets-Sheet 4 INVENTOR JOHN HANDLEY BY W ATTORNEYS United States Patent CAM FOLLOWER MECHANISM John Handley, 39 Wilhelmina Ave.,

Coulsdon, Surrey, England Filed Feb. 5, 1964, Ser. No. 342,636 Claims priority, application Great Britain, Feb. 12, 1963, 5,670/ 63 6 Claims. (CI. 74-54) This invention relates to cams, cam mechanisms, and equipments incorporating cam mechanisms, and has for its object to improve the cfficiency of cams for use in equipment in which the operative load on the cam follower can be in opposite directions at different times.

The main aspect of the invention comprises a cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, and a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to 'be capable of embracing a cam bar therebetween, whereby rotation of either roller causes counterrotation of the other roller.

The term cam bar is to be interpreted as including an endless annular rotatable cam rib and a longitudinally movable cam bar with free ends.

In a cam mechanism utilizing such a cam follower, the rollers will embrace the cam bar with a clearance of the order of one-thousandth of an inch, or 0.025 mm.

Other aspects of the invention consist in cam mechanisms incorporating such follower arms, and mechanical aggregators and disc information storage files incorporating such cam mechanisms.

Yet another aspect of the invention comprises a method of machining an annular or bar cam as aforesaid.

The invention will be understood from the following description of an embodiment shown in the accompanying drawings in which FIG. 1 is a front elevation of a cam assembly incorporating the invention,

FIG. 2 is a cross-sectional plan view of the cam assembly of FIG. 1, while FIG. 3 shows two stages of an aggregate motion linkage operated by a series of cam assemblies as shown in FIGS. 1 and 2, and in turn operating the read heads of a magnetic disc file.

The aggregate motion linkage is that used in my United States application No. 221,920 for operating the read-arms of a magnetic disc file, constituting an information library.

The aggregate motion linkage comprises a series of triangular linkages, each of which consists of two equal links 31, 32, FIG. 3 pivoted together at an apex 33, and having their base ends pivotally connected to the ends of the adjacent links of the preceding and succeeding stages as at 34. The base pivots 34 are guided so as to be able to move to and fro along a base line 35.

The base end 36 of the first link of the first stage is fixed, while the base end 37 of the last link of the last stage is guided for movement along the base line.

The apex 33 of each triangular linkage is slidable on a rod 38 which is parallel to the base-line 35 and is movable at right angles to the base-line between two positions 'by a link 39 from a cam assembly of the kind shown in FIGS. 1 and 2 and described below.

The individual cams and linkages of the successive stages of the aggregator are designed so that the variations in the lengths of the bases of the successive linkages due to the movement of their apices between their two 'ice positions under control of their individual cam assemblies are related in the binary order 1; 2; 4; 8,

It is clear that by operating the respective cams of the aggregator stages according to any binary codes having the same number of bits as there are aggregator stages, the position of the free end 37 of the aggregator reflects the individual code by which the aggregator has been set.

As shown, the free end 37 is pivotally connected to a lever 40 fixed to a shaft 41 which carries the array of read/write arms 42 for a magnetic information storage disc file 43. The arms 42 are set to different circular tracks on the discs 43 according to the binary code in response to which the cams 39 have been operated.

Referring now to FIGS. 1 and 2, the shaft 1 is continuously driven by a toothed belt 2 from an electric motor 3. On the shaft 1 is rotatably mounted a cam disc 4 formed on one side with an annular cam r-ib 5, the inner and outer faces 6, 7 of which constitute complementary cam surfaces. A two-armed cam follower lever 8 is pivoted at 9, and carries two rollers 10, 11, spaced so as to embrace the rib 5 with a clearance of about onethousandth of an inch, so that clockwise or anticlockwise pressure on lever 8 will cause roller 11 or roller 10 respectively to be in functional engagement with cam 5, the other roller in each case being just clear of the adjacent cam surface. The free end 12 of lever 8 is linked to the aggregator mechanism of FIG. 3.

The cam rib 5 is symmetrical about its horizontal center-line, FIG. 1, so that the diametrically-opposed horizontal positions on the cam are equal high points, while the diametrically-opposed vertical positions on the cam are equal low points. Each cam has individual clutch and brake devices for rotating the cam under control of the constantly-rotating shaft, and for stopping the cam at any one of the four high and low positions after a rotation.

As described in my aforesaid specification, each bit of a new binary code for setting the aggregator will be automatically compared with the existing setting of the corresponding cam and its linkage, and the corresponding cams will 'be rotated by 90, only if the new code requires the existing setting of the corresponding linkage to be changed.

Considering one aggregator stage alone, and assuming that the other stages do not move, it will be seen from FIG. 3 that if the apex 33 is to the left, with the rollers 10, 11 on a low position of the corresponding cam 5, and the cam is rotated to a high position, the roller 11 is pressed against the cam surface 7 during the movement. If the apex 33 was originally to the right, and the cam is rotated from a high position to a low position, then the roller 10 is pressed against the cam surface 8 during the movement.

If every movement of every linkage was unidirectional, then no difiiculty would arise. However, since the number of stages to be moved, and the directions in which the selected linkages are to be moved, are quite arbitrary, the complete linkage can undergo a quite complex set of movements in which the effect of the movements of other linkages on a particular linkage, which is itself under change, can result in one or more changes in direction of movement of its apex during the change in the setting of the aggregator. When such changes take place, there will be consequential changes in the direction of the load on follower lever 8, and consequential changeovers of cam control from one face-and-roller to the other face-and-roller.

If now, the roller brought into use by such an arbitrary change, was stationary, or even spinning in the wrong direction, then there would be frictional wear on the cam and roller in bringing the roller into correct rotational relationship with the rotating cam.

However, the spindles 13, 14 of the rollers 10, 11 also carry gear-wheels 15, 16 of such diameter that they are constantly in gear. It is clear that due to the different peripheral lengths of the cam surfaces 6, 7 and the relative movements of the cam 5 and its follower lever 8, the number of teeth on the two gear wheels 15, 16 must differ, and the gear wheels will be designed accordingly.

Whenever one roller is rotating due to its contact with the cam, the other roller is rotated in the opposite direction 'by the gear wheels 15, 16. If now, there is a sudden change of direction of load on the lever 8 during cam rotation, with "a consequent change-over from one roller to the other, the roller which is brought into contact with the cam is already rotating at a linear speed equal to the speed of movement of the cam past the roller, so that there is no relative movement of the two surfaces and no frictional wear.

It is clear that the above form of cam operation is advantageous in any mechanism in which the direction of load on the cam-follower can change during cam operation.

In order to form a rib 5 on a cam disc, so as to obtain the complementary surfaces 6, 7, the outer surface 7 will first be cut to the required contour in conventional fashion. An adjustable cutter is now mounted on a lever such as 8 in place of roller 10, while a hardened roller such as 11 is also mounted on the lever. The cam disc is now mounted on a shaft in the same relative position to lever 8 as shaft 1, FIG. 1, with the rib 5 between the hardened roller and the cutter. The hardened roller is held against the cam surface 7, and the cam surface 6 is cut to the exact complement of the surface 7. Any other method of controlling the cutting of surface 6 direct from surface 7 may be used.

What I claim is:

1. A cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, and a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to be capable of embracing a cam 'bar therebetween, whereby rotation of either roller causes counterrotation of the other roller.

2. An apparatus comprising: a cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to be capable of embracing a cam bar therebetween, and a cooperating annular rib cam bar having inner and outer circumferential surfaces, the outer surface 'being longer than the inner surface, wherein the relative number of teeth on the intermeshed gearwheels depends upon the relative circumferential lengths of the inner and outer cam surfaces with which the cam follower cooperates.

3. An apparatus comprising: a cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to be capable of embracing a cam bar therebetween, a cooperating annular rib cam bar having inner and outer circumferential surfaces, the outer surface being longer than the inner surface, wherein the relative number of teeth on the intermeshed gearwheels depends upon the relative circumferential lengths of the inner and outer cam surfaces with which the cam follower cooperates, and means for moving said cam bar.

4. A method of forming an annular ri-b cam having two cam surfaces for a cam mechanism of the type wherein a follower arm carries two cam followers, one of which is arranged to contact each cam surface of the annular rim cam, comprising the steps of machining one cam surface of the rib cam and then utilising the machined surface as a template for controlling the movement of a lever simulating the follower arm and carrying a roller to follow the machined surface and a tool to cut the other cam surface of the cam rib.

5. A mechanical aggregator comprising a plurality of mechanical devices, each having a mechanical output which represents a controllable function of a mechanical input, arranged in tandem where the input of a first device is dependent upon the output of a second device; and a plurality of cam mechanisms one for each mechanical device for controlling the function of the corresponding device, each cam mechanism comprising a cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, and a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to be capable of embracing a cam bar therebetween; whereby the output of the first device is a function of the input of the second device and the positions of the corresponding cam bars.

6. An information file comprising: at least one recording medium on a rotatable shaft, at least one read arm for accessing at least one recording medium; a mechanical aggregator comprising: a plurality of mechanical devices, each having a mechanical output which represents a controllable function of a mechanical input, arranged in tandem where the input of a first device is dependent upon the output of a second device; and a plurality of cam mechanisms controlling the function of the corresponding device, each cam mechanism comprising a cam follower arm carrying a pair of spaced parallel spindles, a pair of rotatable coplanar intermeshing gearwheels mounted one on each spindle, and a pair of coplanar cam rollers which are mounted one on each said spindle which are rotatably fixed one to each gearwheel and which are of smaller diameter than said gearwheels so as to be capable of embracing a cam bar therebetween; and a linkage between the output of the first device and the arm, whereby the position of said arm is controlled by said mechanical aggregator.

References Cited by the Examiner UNITED STATES PATENTS 138,130 4/1873 Clisbee 74-54 780,130 1/ 1905 Salzer et al.

810,353 1/1906 Salzer et al 74569 2,552,350 5/1951 Smith 7456 2,800,642 7/1957 May.

3,124,789 3/ 1964 Wasylenko.

FOREIGN PATENTS 801,599 5/1936 France.

MILTON KAUFMAN, Primary Examiner. BROUGHTON G. DURHAM, Examiner.

D. H. THIEL, Assistant Examiner. 

1. AN CAM FOLLOWER ARM CARRYING A PAIR OF SPACED PARALLEL SPINDLES, A PAIR OF ROTATABLE COPLANAR INTERMESHING GEARWHEELS MOUNTED ONE ON EACH SPINDLE, AND A PAIR OF COPLANAR CAM ROLLERS WHICH ARE MOUNTED ONE ON EACH SAID SPINDLE WHICH ARE ROTATABLY FIXED ONE TO EACH GEARWHEEL AND WHICH ARE OF SMALLAR DIAMETER THAN SAID GEARWHEELS SO AS TO BE CAPABLE OF EMBRACING A CAM BAR THEREBETWEEN, WHEREBY ROTATION OF EITHER ROLLER CAUSES COUNTERROTATION OF THE OTHER ROLLER. 